Modular and lightweight myoelectric prosthesis components and related methods

ABSTRACT

Prosthetic devices and, more particularly, modular myoelectric prosthesis components and related methods, are described. In one embodiment, a hand for a prosthetic limb may comprise a rotor-motor; a transmission, comprising a differential roller screw; a linkage coupled to the transmission; and at least one finger coupled to the linkage. In one embodiment, a component part of a wrist of a prosthetic limb may comprise an exterior-rotor motor, a planetary gear transmission, a clutch, and a cycloid transmission. In one embodiment, an elbow for a prosthetic limb may comprise an exterior-rotor motor, and a transmission comprising a planetary gear transmission, a non-backdrivable clutch, and a screw.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication 61/935,836, filed on Feb. 4, 2014, which is incorporatedherein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under W81XWH-11-1-0720and W81XWH-10-2-0033 awarded by the United States Army. The governmenthas certain rights in the invention.

TECHNICAL FIELD

The present disclosure is generally directed to prosthetic devices and,more particularly, to modular myoelectric prosthesis components andrelated methods.

BACKGROUND

Amputation of the arm causes significant disability, which is mosteffectively treated by replacement of the missing limb with a prostheticdevice. Body-powered prostheses use a Bowden cable that couples motionof an intact joint to movement of the terminal device. Myoelectricprostheses control motorized joints via commands sent through thepatients' residual muscles and sensed by surface electrodes embedded inthe prosthetic socket.

Advances in embedded controllers, battery density, and motor design haveincreased the number of myoelectric prosthesis users. However, existingmyoelectric prostheses are heavy, and wearing them constantly does notappeal to many amputees. Additionally, such prostheses are often toolarge for many amputees, such as children and many women. Severalmulti-function arms have recently come on the market, including OttoBock's Michelangelo Hand, the Touch Bionics Hand, the BeBionics Hand,and the Vincent Hand. These devices are typically designed for a 50thpercentile male (22.2 cm/8.75″ hand circumference). Other hands arebeing developed in research, but use components that limit the strength,weight, and small volumes the limbs can achieve.

SUMMARY

In one embodiment, a hand for a prosthetic limb may comprise arotor-motor; a transmission, comprising a differential roller screw; alinkage coupled to the transmission; at least one finger coupled to thelinkage; wherein the rotor-motor is configured to actuate thetransmission, the transmission is configured to actuate the linkage, andthe linkage is configured to flex or extend the at least one finger. Atleast one finger of the hand may comprise an index finger and middlefinger. The index finger and the middle finger may be fused. At leastone finger may comprise an independently hinged finger, such as a ringfinger or a pinky finger. The hand may comprise a side bar coupled tothe transmission for transmitting motion to at least one of theindependently hinged fingers. The linkage of the hand may generate ananatomically natural motion. The hand may further comprise a controllerfor the control of the hand. The hand may comprise an exoskeleton, whichmay be made from aluminium. A portion of the exoskeleton may beattachable to a wrist flexor. The rotor-motor of the hand may be abrushless interior rotor motor. The transmission of the hand may furthercomprise a gear set comprising at least one gear, the gear setpositioned between the rotor-motor and the differential roller screw,the gear set adapted to translate rotational motion from the rotor-motorinto linear motion of the differential roller screw. The transmissionmay further comprise a non-backdrivable clutch. The clutch may comprisea cam comprising an annulus, an input side that is adapted to receive aninput force, and an output side that is adapted to provide an outputforce; a pin and a roller, each located adjacent to the input side ofthe cam; wherein the cam is adapted so that movement of the cam inresponse to the input force causes the pin to push the roller out ofcontact with the annulus, when a force is applied to the input side ofthe cam, the pin pushes the roller out of contact with the annulus toallow for movement of the cam. The transmission may further comprise agear set comprising at least one gear, the gear set positioned betweenthe rotor-motor and the differential roller screw, the gear set adaptedto translate rotational motion from the rotor-motor into linear motionof the differential roller screw. The hand may further comprising acasing for housing the differential roller screw. The cam may bepositioned at the base of the hand, the casing may have a proximal endthat is adjacent to the cam, and the casing may be positioned in theinterior of the hand. The clutch may further comprise a mechanical fuse.The linkage of the hand may be coupled to the transmission via a pivot.The hand may further comprise a thumb comprising exactly one motor and agear set comprising at least one gear, wherein the motor actuates onlythe thumb. The hand may be adapted to be positioned in more than one, orin all, of the following positions: relaxed, palm-flat, chuck grip, andcylindrical grip.

In one embodiment, a wrist for a prosthetic limb may comprise a wristrotator comprising a first exterior-rotor motor, a first planetary geartransmission, a first clutch and a first cycloid transmission, in atransmission arrangement such that actuation of the first exterior-rotormotor causes movement through the first planetary gear transmission,first clutch, and first cycloid transmission to cause rotation of thewrist; and a wrist flexor comprising a second exterior-rotor motor, asecond planetary gear transmission, a second clutch and a second cycloidtransmission, in a transmission arrangement such that actuation of thesecond exterior-rotor motor causes movement through the second planetarygear transmission second first clutch, and second cycloid transmissionto cause flexion of the wrist. The first clutch may comprise anon-backdrivable mechanism for preventing output motion of the firstclutch to be transmitted to the first cycloid transmission. The secondclutch may comprise a non-backdrivable mechanism for preventing outputmotion of the first clutch to be transmitted to the first cycloidtransmission. At least one of the first planetary gear transmission andthe second planetary gear transmission may be a single-stage planetarygear transmission. The torque ratio of the first planetary geartransmission may be about 3.71:1 and the torque ratio of the firstcycloid transmission may be about 16:1. The wrist may comprise aninterface on the wrist rotator for transmitting signals across an accessof rotation of the wrist rotator. The interface may comprise aninterface for power signals and an interface for ground signals. Theinterface may further comprise an interface for at least twocommunication signals. The wrist may comprise a mechanical stop to limitmotion of the wrist flexor. The wrist rotator and the wrist flexor maybe connected by a coupler that allows for the transmission of power fromthe wrist rotator to the wrist flexor. The wrist flexor may be set on arotation axis skewed by between about 10 to 30 degrees to provideradial/ulnar deviation. The non-backdrivable mechanism may comprise aplurality of rollers and a plurality of springs.

In one embodiment, a component part of a wrist of a prosthetic limb maycomprise an exterior-rotor motor, a planetary gear transmission, aclutch, and a cycloid transmission. The exterior-rotor motor, aplanetary gear transmission, a clutch, and a cycloid transmission may bein a transmission arrangement such that actuation of the exterior-rotormotor causes movement through the planetary gear transmission, clutch,and cycloid transmission to cause movement of the wrist. The clutch maycomprise a non-backdrivable mechanism for preventing output motion ofthe clutch to be transmitted to the cycloid transmission. The planetarygear transmission may be a single-stage planetary gear transmission. Themovement of the wrist may be a rotational movement. The torque ratio ofthe planetary gear transmission may be about 3.71:1 and the torque ratioof the cycloid transmission may be about 16:1. The movement of the wristmay be a flexion movement. The wrist component may be set on a rotationaxis skewed by between about 10 to 30 degrees to provide radial/ulnardeviation.

In one embodiment, an elbow for a prosthetic limb may comprise anexterior-rotor motor; and a transmission comprising a planetary geartransmission, a non-backdrivable clutch, and a screw. The screw may beadapted to receive a rotational force in a first direction from theclutch, and in response to the rotational force in the first direction,extend linearly with respect to the transmission so as to cause theelbow to flex. The clutch may comprise a cam comprising an annulus, aninput side that is adapted to receive an input force, and an output sidethat is adapted to provide an output force; and a pin and a roller, eachlocated adjacent to the input side of the cam. The cam may be adapted sothat movement of the cam in response to the input force causes the pinto push the roller out of contact with the annulus, when a force isapplied to the input side of the cam, the pin pushes the roller out ofcontact with the annulus to allow for movement of the cam. The elbow maycomprise a frame adapted to surround the transmission and having anopening for receiving a battery; a socket connector coupled to theelbow, for attaching the elbow to a prosthetic socket; and a positionsensor for indicating the rotational movement of the elbow. The screwmay be further adapted to receive a rotational force in a seconddirection from the clutch, and in response to the rotational force inthe second direction, retract linearly with respect to the transmissionso as to cause the elbow to extend. The socket connector may be coupledto the elbow at a carrying angle. The screw may be a differential rollerscrew. The elbow may comprise a pivot for the flexion or extension ofthe elbow. The pivot may be encased in a bushing made of a nonlinearcompliant material. The elbow may have a 135 degree range of motionbetween full flexion and full extension. The elbow may further comprisea shear pin. The elbow may further comprise a first limb portion and asecond limb portion coupled together at an elbow joint. A first end ofthe screw may be coupled to the first limb portion at a bracket. Thetransmission may be coupled to the second limb portion at a transmissionjoint. When the screw extends and retracts linearly, the screw may pivotwith respect to the bracket. The transmission may pivot with respect tothe second limb portion.

In one embodiment, an elbow component for a prosthetic limb may comprisea first limb portion and a second limb portion coupled together at anelbow joint. The transmission may comprise a screw. A first end of thescrew may be coupled to the first limb portion at a bracket. Thetransmission may be coupled to the second limb portion at a transmissionjoint. The screw and the hinge may be adapted so that when the screwextends linearly in a direction away from the transmission, the screwmay apply a force on the bracket that causes the first limb portion torotate about the elbow joint towards the second limb portion. The screwand the hinge may be adapted so that when the screw retracts linearly ina direction towards the transmission, the screw may apply a force on thebracket that causes the first limb portion to rotate about the elbowjoint away from the second limb portion. The transmission and the elbowjoint may be adapted so that when the screw extends linearly in adirection away from the transmission, the transmission may rotate aboutthe transmission joint in a first direction. The transmission and theelbow joint may be adapted so that when the screw retracts linearly in adirection towards the transmission, the transmission may rotate aboutthe transmission joint in a second direction opposite to the firstdirection. When the screw extends and retracts linearly, the screw maypivot with respect to the bracket and the transmission may pivot withrespect to the second limb portion. The screw may extend and retract inresponse to actuation of the transmission. The elbow component maycomprise a position sensor to indicate rotational movement of the elbowcomponent. The elbow component may comprise a bushing made of anonlinear compliant material that encases the transmission pivot; asocket connector coupled to either the first limb portion or the secondlimb portion; and a frame that surrounds the transmission and is adaptedto receive a battery. The screw may be a differential roller screw. Thesocket connector may be coupled to the first limb portion at a carryingangle. The screw may be coupled to the bracket by a nut.

In one embodiment, a transmission for an elbow joint of a prostheticlimb may comprise a motor, a gear set comprising at least one gear, anon-backdrivable clutch, and a screw, adapted to be housed in a framepivotally attached to a second portion of the limb. The screw may beadapted to be coupled to a first portion of the limb that is pivotablewith respect to the second portion of the limb. The screw may be adaptedto receive a rotational force in a first direction from the clutch, andin response to the rotational force in the first direction, extendlinearly with respect to the transmission. The screw may be adapted toreceive a rotational force in a second direction from the clutch, and inresponse to the rotational force in the second direction, retractlinearly with respect to the transmission. The non-backdrivable clutchmay comprise a cam comprising an annulus, an input side that is adaptedto receive an input force, and an output side that is adapted to providean output force; and a pin and a roller, each located adjacent to theinput side of the cam. The cam may be adapted so that movement of thecam in response to the input force causes the pin to push the roller outof contact with the annulus, and when a force is applied to the inputside of the cam, the pin pushes the roller out of contact with theannulus to allow for movement of the cam. The screw may be adifferential roller screw.

The features described above are available in different embodiments ofthe prosthetic components described, and should not be interpreted tolimit or narrow the scope of the claims. The features described hereinmay additionally be applied in different combinations in differentembodiments.

DRAWINGS

While the appended claims set forth the features of the presenttechniques with particularity, these techniques may be best understoodfrom the following detailed description taken in conjunction with theaccompanying drawings of which:

FIG. 1 is a lateral view of a prosthetic limb according to anembodiment.

FIG. 2 is an anterior view of a prosthetic limb, according to anembodiment.

FIG. 3 is a cut-away anterior view of the prosthetic limb, according toan embodiment.

FIG. 4 is a cut away posterior view of the prosthetic limb, according toan embodiment.

FIG. 5 is a posterior view of a hand of the prosthetic limb, accordingto an embodiment.

FIG. 6 is a proximal view of the hand of the prosthetic limb, showing apossible implementation of a non-backdrivable clutch.

FIG. 7 is a cross-section lateral view of the hand of the prostheticlimb, according to an embodiment.

FIG. 8 is an anterior view of the hand of the prosthetic limb, accordingto an embodiment.

FIG. 9 shows the hand of the prosthetic limb in a relaxed posture,according to an embodiment.

FIG. 10 shows the hand of the prosthetic limb in a palm-flat posture,according to an embodiment.

FIG. 11 shows the hand of the prosthetic limb in a chuck grip posture,according to an embodiment.

FIG. 12 shows the hand of the prosthetic limb in a cylindrical gripposture, according to an embodiment.

FIG. 13 is an exploded view of the planetary gear transmission,non-backdrivable clutch, and cycloid transmission components of thewrist rotator of the prosthetic limb, according to an embodiment.

FIG. 14 is a cross-section view of the wrist rotator of the prostheticlimb, according to an embodiment.

FIG. 15 is a lateral view of the elbow of the prosthetic limb, accordingto an embodiment.

FIG. 16 is a cross-section view of the elbow of the prosthetic limb,according to an embodiment.

FIG. 17 shows the elbow of the prosthetic limb in an extended position,according to an embodiment.

FIG. 18 shows the elbow of the prosthetic limb in a flexed position,according to an embodiment.

FIG. 19 shows a perspective view of the elbow of the prosthetic limb,according to one embodiment.

FIG. 20 shows a side view of the elbow of the prosthetic limb, accordingto one embodiment.

DESCRIPTION

Turning to the drawings, wherein like reference numerals refer to likeelements, the following description is based on embodiments of theclaims and should not be taken as limiting the claims with regard toalternative embodiments that are not explicitly described herein.

Embodiments described herein relate to a modular and lightweightprosthetic limb and its modular components. In one embodiment, theprosthetic limb delivers specified torques and motion profiles utilizingits small size, small mass, durable design, and specified axisrotations. The arm maintains different motion profiles, each of whichmay vary the position, speed, and/or acceleration of its variouscomponents. The limb is modular, allowing a user to either use all ofthe components described herein or swap them out for alternate parts.Different components of the limb may use exterior-rotator motors, whichhave their rotor on the outside of the stator, as described, forexample, in Sensinger, Clark & Schorsch, “Exterior vs. Interior rotorsin robotic brushless motors,” in IEEE Conference on Robotics andAutomation, Shanghai China, 2011, pp. 2764-2770.

FIG. 1 shows a lateral view of a prosthetic limb 10 (“limb 10”). Thecomponents of the limb 10 shown in FIG. 1 include a universal coupler20, a hand 30, a forearm 150, an elbow 50, a wrist flexor 70, and awrist rotator 90. The limb 10 further includes a socket connector 95that connects to the distal end of a user's prosthetic socket (notshown). The hand 30, the wrist flexor 70, the wrist rotator 90, and theelbow 50 are modular, allowing clinicians to provide an amputee userwith only the components he or she needs based on his or her level ofamputation. For example, a below-elbow amputee, whose arm still has theelbow, would not need the elbow 50 component. Each modular component isconnected by a CAN bus communication standard for prosthetic arms and auniversal coupler 20, allowing users to swap different hands fordifferent applications such as an electric hook, a lightweight hand, ora more powerful hand. The universal coupler 20 allows a user to attach,detach, spin, and lock in a component of the arm. One possibleembodiment of the universal coupler 20 is described in Sutton, Clawson,et al, “Towards a universal coupler design for modern poweredprostheses,” Myoelectric Controls Symposium, Fredericton, Canada, 2011.

In one embodiment, the limb 10 may be covered by a cosmesis to provideprotection from liquids and dirt, and to result in appearing as anatural limb.

FIG. 3 shows a cut-away anterior view of the limb 10 and FIG. 4 shows acut-away posterior view of the limb 10. Four batteries 101 that providepower to the limb 10 are housed in a forearm 150. In one embodiment,each battery 101 is a 14.8V Tenergy Li-Ion 18500 Cylindrical 3.7V 1400mAh with tabs from All-Battery. In other embodiments, the batteries 101could be housed externally to the limb 10, for instance on a user'sbelt. As shown in FIG. 4, a master controller 102 is housed on top ofthe hand 30.

In one embodiment, the master controller 102 is housed in the forearm150 and controls the movement of fingers 350, a thumb 360, the wristflexor 70, the wrist rotator 90, and the elbow 50. The master controller102 may be programmed with a pattern recognition module, a directcontrol module, or another module known in the art in order to causedifferent components of the limb 10 to move. In one embodiment, themaster controller 102 is programmed with a control module, modified fromsmall motor controller software obtained under license from the JohnsHopkins University Applied Physics Laboratory (Laurel, Md.) to allow CANcommunication. The master controller 102 may record user signals fromsensors 26 coupled to a user's socket 25. The sensors 26 may be EMGsensors or other appropriate sensors. The master microcontroller 102uses a 4-wire CAN bus to communicate the movements of the components ofthe limb 10.

A flexible circuit 395 is coupled to the master controller 102 forcommunication to and from the master controller 102. Where the limb 10makes use of pattern recognition control using EMG signals, the mastercontroller 102 communicates with the sensors 26 in the user's socket 25(not shown) to train the pattern recognition control module and tooperate the limb 10. A training switch 107 switches the limb 10 betweena training mode, in which information collected from the sensors 26train the pattern recognition module, and an operating mode, in whichinformation collected from the sensors 26 are used by the mastercontroller 102 to move different components of the limb 10, includingthe elbow 50, the wrist rotator 90, the wrist flexor 70, the fingers350, and the thumb 360. Wire connectors for power, ground, andcommunication signals (not shown) extend from the proximal end of thesocket connector 95 for connection with the appropriate electrodes atthe user's socket 25.

As shown in FIG. 3, in one embodiment the forearm 150 also may house asecondary controller 103. In one embodiment, the secondary controller103 may control the movement of the elbow 50 and the wrist rotator 90.Such a configuration can be useful when the universal coupler 20 isreleased and the master controller 120 is separated, along with thewrist flexor 70 and the hand 30, from the rest of the limb 10. An elbowboard 104 controls an exterior-rotor motor 510 and a rotator board 105controls an exterior-rotor motor 910.

Hand. As shown in FIG. 5, the hand 30 is a modular component thatcomprises an endoskeleton 370, the fingers 350, the thumb 360,hand-motor motor-amplifiers (not shown), and the master controller 102.The endoskeleton 370 is fastened to the output of the wrist flexor 70.In one embodiment, the endoskeleton 370 is made of aluminum or anothersuitable lightweight material. The endoskeleton 370 supports the fingers350 and the thumb 360. The endoskeleton 370 also houses the hand-motormotor-amplifiers and a hand microcontroller (not shown), which areembedded in the master controller 102. The hand 30 further comprises arotor motor 310, a planetary gear transmission 320, a non-backdrivableclutch 330, a differential roller screw 340, and a finger linkage 355.In one embodiment, the rotor motor 310 is a brushless interior rotormotor and is coupled to the planetary gear transmission 320.

The rotor motor 310 and the planetary gear transmission 320 actuate apinion gear 371, which actuates a finger gear 372. The finger gear 372is connected to pins 331, which extend into a clutch 330 to drive theclutch 330. FIG. 6 shows the clutch 330 as a non-backdrivable clutchlocated at the proximate end of the hand 30. The clutch 330 in thisembodiment comprises an annulus 332, rollers 333, an output cam 334, andsprings 336. The springs 336 ensure that the rollers 333 are in contactwith the annulus 332 when the clutch 330 is not being driven. As afinger gear 372 turns to actuate the clutch 330, the pins 331 push therollers 333 out of contact with the annulus 332, allowing the output cam334 to turn. The pins 331 also engage protrusions 335 on the output cam334. Motion of the output cam 334 occurs when the pins 331 push therollers 333 out of contact with the annulus 332 before they engage theprotrusions 335 on the output cam 334. If movement is attempted from theoutput side of the clutch 330 without pushing the rollers 333 out of theway, the jam angle between the grounded annulus 332, the rollers 333,and the output cam 334 prevents motion from occurring. The annulus 332includes a mechanical fuse (not shown) to prevent excessive torqueapplied to the fingers 350 from damaging the rotor motor 310. Forinstance, if the user falls on the hand 30, the mechanical fuse failsand may be replaced with relative ease.

FIG. 7 is a cross-section lateral view of the hand 30. The differentialroller screw 340 is housed in a casing 341 that prevents bending momentsupon the differential roller screw 340. A thrust bearing 342 preventsaxial loads from the differential roller screw 340 from beingtransmitted to the clutch 330. The differential roller screw 340 isaffixed via a pivot 343 to a linkage connector 351, which in turnconnects to a linkage 352 of the fingers 350. The linkage 352 comprisesa first link 352 a, a second link 352 b, a third link 352 c, and a link352 d to ground, as shown in FIG. 5. The rotational motion of the outputcam 334 causes the differential roller screw 340 to thread through thecasing 341, causing a roller screw nut 343 to move distally orproximally in response to motion of output cam 334. The linkageconnector 351 moves in response to movement from the roller screw nut343, which in turn activates the linkage 352, causing the fingers 350 toflex and extend.

FIG. 8 shows an anterior view of the hand 30. A side arm 353 projectsfrom the differential roller screw 340 to transmit motion to a ringfinger 350 c and a pinky finger 350 d via lateral finger springs 354.The linkage 352 transmits motion from the differential roller screw 340to the fingers 350 without creating a bending moment on the differentialroller screw 340. FIG. 8 also shows the fingers 350. Each finger 350 a,350 b, 350 c, and 350 d employs the linkage 352—a four-bar linkage inthe illustrated embodiment. The linkage 352 couples flexion of themetacarpophalangeal joint (“MCP”) to flexion of the proximalinterphalangeal joint (“PIP”) joint. This four-bar linkage geometry isoptimized to provide maximal pinch-force to motor torque ratio, withinspatial and mechanical constraints, while generating motion that isanatomically natural. Linkages for each finger 350 are shown at FIG. 5,where the linkage 352 for the index finger 350 a is labeled. The linkconnecting the frame to the distal phalange in each finger is designedwith longitudinal compliance, resulting in approximately 5 degrees ofcompliance at the PIP joint for the index finger 350 a and the middlefinger 350 b. In one embodiment, the proximal phalanges of the indexfinger 350 a and the middle finger 350 b are fused together forrigidity. The ring finger 350 c and the pinky finger 350 d are eachindependently hinged, and coupled via compliant springs 354 to the sidearm 353. Having the ring finger 350 c and the pinky finger 350 dindependently hinged allows for them to move with the index and middlefingers 350 a and 350 b, and to generate a conformal grasp by the hand30.

Thumb. In one embodiment, the thumb 360 comprises its own rotor motor361 coupled to a planetary gear 362. According to an embodiment, thethumb 360 is independently powered from the finger 350 and is driven bythe rotor motor 361 and planetary gear 362 so as to act independently ofthe fingers 350. Having an independent thumb 360 increases the stabilityof the gripping ability of the hand 30. The thumb 360 has a singledegree of freedom. In one embodiment, the rotor motor 361 is a brushlessinterior rotor motor, model EC10 from Maxon Precision Motors, Inc. (FallRiver, Mass.), which is coupled to the planetary gear transmission 362offered by the same company. Movement is transmitted from the planetarygear transmission 362 to the thumb 360 via a worm pinion 363 thatinterfaces with a worm gear 364. In one embodiment, the worm gear 364 isa custom, off-axis helical worm gear, made of brass. In one embodiment,shown in FIG. 5, the worm gear 364 is positioned posterior to the wormpinion 363. The worm gear 364 converts motion from the worm pinion 363to the rotation axis of the thumb 360. The axis of the thumb 360 ispositioned such that the thumb 360 may provide multiple different handpostures with a single degree of freedom. These postures include relaxed(shown at FIG. 9), palm-flat (shown at FIG. 10) chuck grip (shown atFIG. 11), and cylindrical grip (shown at FIG. 12). To fit the rotormotor 361 and the thumb transmission (including the planetary gear 362and the worm pinion 363) within the hand 30 profile, the axis of theworm pinion 363 is skewed by approximately 20 degrees. The tooth profileof the worm gear 364 allows for proper meshing with the skewed positionof the worm pinion 363. A position sensor 365 senses the position of thethumb 360, and information from the position sensor 365 is used by themaster controller 102 for position control of the thumb 360. In oneembodiment, the position sensor 365 is a magnetic hall-effect sensor,shown in FIG. 5.

Wrist. In an embodiment, the wrist of the limb 10 has two degrees offreedom: rotation from the wrist rotator 90 and flexion from the wristflexor 70. Each of the wrist rotator 90 and the wrist flexor 70 is awrist component. The wrist rotator 90 comprises an exterior-rotor motor910, a planetary gear transmission 920, a non-backdrivable clutch 930,and a cycloid transmission 940. In one embodiment, shown in FIGS. 1-4,the wrist rotator 90 has an outer diameter of 20 mm and a length of 13mm. In one embodiment, insulation material is made of Paralyne with aninsulation thickness of 0.0508 nm. The wrist rotator may utilize asupply voltage of 14.8V and a supply current of 4 A from batteries 101,and include WYE termination and a net fill factor of 65%. Seals may beapplied to the wrist flexor 70 and the wrist rotator 90 to make themwater-resistant.

The wrist rotator 90 is powered by the exterior-rotor motor 910, whichin one embodiment is a DC brushless motor. Magnets are placed at theends of each tooth, radial to the center of the motor's stator. In oneembodiment, 14 magnets are placed distally around the center of thestator. The magnets are arranged in an alternating pole arrangement,where each magnet's pole is opposite to its neighbor. Each stator toothis wrapped with three-phase, single span windings resulting in threesets of wires looped around the stator. The winding pattern isAacCBbaACcbB, where capital letters denote clockwise winding andlower-case letters denote counter-clockwise winding, and A, B, and Cdenote the three phases.

In one embodiment, the exterior-rotator motor 910 is controlled by themaster controller 102. In other embodiments, where the master controller102 is not available in the hand 30, the exterior-rotator motor 910 maybe controlled by the secondary controller 103. The control module oneither the master controller 102 or the secondary controller 103 timeswhen current should run through each motor winding of theexterior-rotator motor 910 and sends a signal to FETs to drive theexterior-rotator motor 910.

The exterior-rotator motor 910 is connected to a planetary geartransmission 920, shown in FIG. 13. The planetary gear transmission 920comprises a grounded annulus 924, a sun gear (input) 925 fastened to themotor output, planetary gears 921, and a carrier plate (output) 926. Inone embodiment, the planetary gear transmission 920 is a modified1-stage planetary gear modified from a stock MicroMo gear (16/7 246:1).In other embodiments, the planetary gear transmission 920 may comprise a2-stage planetary gear.

The output of planetary gear transmission 920 is coupled to anon-backdrivable clutch 930, also shown at FIG. 13. In one embodiment,the non-backdrivable clutch 930 allows motion from the planetary geartransmission 920 to be transmitted to the non-backdrivable clutch 930output in either direction, clockwise or counter-clockwise, butinherently prevents any additional movement from the output of thenon-backdrivable clutch 930 to be transmitted to the input of thecycloid transmission 940, thus allowing the actuation unit (i.e., theplanetary gear transmission 920, the non-backdrivable clutch 930, andthe cycloid transmission 940) to maintain a position without requiringconstant power consumption from the motor, as described further in M.Controzzi, C. Cipriani, M. C. Carrozza. Miniaturized non-back-drivablemechanism for robotic applications, Mechanism and Machine Theory,Elsevier, vol. 45, no. 10, pp. 1395-1406, 2010. This locking featureallows a user to carry a heavy object, such as a grocery bag, withoutthe batteries 101 needing to supply power to the motors to keep theobject lifter. As a result, the wrist rotator 90 is capable of passivelyholding more force than it can actively generate.

As shown in FIG. 13, the non-backdrivable clutch 930 comprises an inputplate 931, a grounded annulus 932 (encapsulating the clutch 930, and notshown), four rollers 933, an output cam 934, and two springs 935 thatensure the rollers 933 are in contact with the ground. Pins 936 on theinput plate 931 push the rollers 933 out of contact with the groundedannulus 932. The pins 936 on the input plate 931 also engage protrusions937 on the output cam 934. Motion of the non-backdrivable clutch 930occurs when the pins 936 push rollers 933 out of contact with thegrounded annulus 932 before the pins 936 engage the protrusions 937 onoutput cam 934. If movement is attempted from the output side of thenon-backdrivable clutch 930 without pushing the rollers 933 out of theway, the jam angle between the grounded annulus 932, the rollers 933,and the output cam 934 prevents motion of the non-backdrivable clutch930 from occurring.

Still with respect to FIG. 13, the output of the non-backdrivable clutch930 is connected to a cycloid transmission 940, as described further inreferences J. W. Sensinger, “Efficiency of High-Sensitivity Gear Trains,Such as Cycloid Drives,” J. Mech. Des. 135(7), 071006 (2013) (9 pages);Del Castillo, J. M., 2002, “The Analytical Expression of the Efficiencyof Planetary. Gear Trains,” Mech. Mach. Theory, 37(2), pp. 197-214,2002; and J. W. Sensinger, Unified Approach to Cycloid Drive Profile,Stress, and Efficiency Operation,” J. Mech. Des. 132(2), 024503 (2010)(5 pages). The cycloid transmission 940 comprises a grounded annulus(not shown) that houses a set of freely spinning rollers 943, aneccentric input cam 941, a cycloid disk 944, and an output carrier plate945. In one embodiment, parameters of the cycloid transmission 940 maybe optimized so that the torque ratio of the cycloid transmission 940 is16:1 and its outer diameter is 23 mm. As a result of these constraints,the input eccentricity of the cycloid transmission 940 is 0.57 mm, itsroller diameter is 1 mm, and its roller offset diameter is 20 mm. Theseparameters are optimized to provide minimum radial loading whilemaintaining a design without undercutting the gear-tooth profile. Thecycloid disk 944 profile may be determined using the methods set out inreference J. W. Sensinger, Unified Approach to Cycloid Drive Profile,Stress, and Efficiency Operation,” J. Mech. Des. 132(2), 024503 (2010)(5 pages). A counter-weight 946 is also shown in FIG. 13. In anembodiment, the counter-weight 946 is attached to the eccentric inputshaft 947 at 180° out of phase with the cycloid disk 944, so as tocancel out oscillatory vibrations. FIG. 14 displays a cross section viewof the transmission components of the wrist rotator 90. It should beunderstood that although one embodiment of planetary gear transmission920, non-backdrivable clutch 930, and cycloid transmission 940 isdetailed here, other embodiments would be apparent to one of ordinaryskill in the art. As shown in FIG. 14, the plate 91 may be configured tobe coupled to the frame of the hand 30. Housing 93 provides a cover tothe wrist rotator 90 and may be made of plastic or another suitablematerial. A connector 92 may be configured to connect to the output ofthe wrist flexor 70, so as to transfer the flexion/extension motionproduced by the wrist flexor 70 through the wrist rotator 90 and to thehand 30, along a flexor axis 95, shown in FIG. 14. Actuation of thetransmission of the wrist rotator 90 causes the wrist rotator 90 torotate around a rotator axis 94 along the a cycloid output 750 (shown inFIG. 2).

In one embodiment, contribution of increasing the torque was balancedbetween the torque ratios of the planetary gear transmission 920(3.71:1) and the cycloid transmission 940 (16:1) using the knownefficiency of both mechanisms as set out in J. W. Sensinger, “Efficiencyof High-Sensitivity Gear Trains, Such as Cycloid Drives,” J. Mech. Des.135(7), 071006 (2013) (9 pages) and Del Castillo, J. M., 2002, “TheAnalytical Expression of the Efficiency of Planetary. Gear Trains,”Mech. Mach. Theory, 37(2), pp. 197-214, 2002, in order to maximize thetotal torque produced by wrist rotator 90 while ensuring a reasonablylow stress on the components of the wrist rotator 90.

The distal end of the wrist rotator 90 includes a bulls-eye pattern offour copper ring interfaces, for transmitting four signals across theaxis of rotation of the wrist rotator 90. In one embodiment, one of theinterfaces transmits power, two of the interfaces transmit communicationsignals, and one of the interfaces acts as an electrical ground. Theproximal end of the wrist flexor 70 includes multiple conductive pins.When the wrist flexor 70 is coupled to the wrist rotator 90, and thelimb 10 is in training mode or operating mode, the multiple conductivepins provide power from the batteries 101 to the wrist flexor 70 and thehand 30. The concentric pattern of copper ring interfaces, and theirconnection to the spring-loaded pins, allow for continuous operation ofthe limb 10 while the wrist rotator 90 is rotating. The distal portionof the wrist rotator 90 is the proximal side of the universal coupler20, which allows the wrist to be interchanged with a variety of handunits. In other embodiment, a battery powering hand 30 could be housedin hand 30.

Wrist flexor. In an embodiment, the wrist flexor 70 utilizes the samedrivetrain design used in the wrist rotator 90, described herein,including the exterior-rotor motor 910, the planetary gear transmission920, the non-backdrivable clutch 930, and the cycloid transmission 940.The wrist flexor 70 uses a flexible circuit (not shown) to passelectrical signals, including signals to and from the master controller102 and the secondary controller 103, across its axis of rotation. FIG.2 shows an anterior view of the limb 10, including a view of the wristflexor 70. The wrist flexor 70 has a range of motion limited by amechanical stop 770. The wrist flexor 70 is of modular design and iscoupled to the wrist rotator 90 by the universal coupler 20. Theproximal portion of the wrist flexor 70 is the distal portion of theuniversal coupler 20. The wrist flexor 70 includes a shear pin (notshown) that breaks at a specified excessive torque, which limits damageto the wrist flexor 70 if the user falls and lands on the wrist flexor70 or if the wrist flexor 70 is the subject of other accidental force.

The rotation axis of the wrist flexor 70 actuates primarily in thedirection of flexion and extension. The axis location is skewed by 10-30degrees to provide radial/ulnar deviation in addition to the primaryflexion/extension directions of motion. This results a movement known asa dart-thrower motion that has been found to be the most common movementin activities of daily living. The wrist flexor 70 and the wrist rotator90 could be coupled to the hand 30, or to another commercially availableprosthetic hand, such as the Transcarpal Hand offered by Ottobock(Duderstadt, Germany).

Elbow. In one embodiment, the elbow 50 is a modular unit that providesflexion and extension about the elbow axis. The elbow 50 generatesmovement of the forearm 150 in response to a command of the user.

FIG. 15 shows a lateral view of the elbow 50. In one embodiment, theelbow 50 is connected to the frame 110, which has openings for thebatteries 101 (not shown in FIG. 15). An on/off switch 108 for the limb10 is coupled to the frame 110. The frame 110 surrounds a transmissionhousing 550 and supports an elbow hinge joint 130 and a bushing 120. Aposition sensor 585 indicates rotational movement of elbow 50. In oneembodiment, the position sensor 585 is a magnetic hall-effect sensor.The axis of rotation of the elbow 50 is shown by the line 560. Thedistal end of the elbow 50 is coupled to the socket connector 95. Theflexion axis is offset ventrally to the limb center. This allowsadditional components to be packaged in the elbow space, but leaves agap when the elbow is fully flexed. This gap may be covered by acompliant covering, such as rubber or fabric.

FIG. 16 shows a cross-section view of the elbow 50. The elbow 50comprises an exterior-rotor motor 510. In an embodiment, theexterior-rotator motor is of the same design as the exterior-rotor motorused in the wrist rotator 90. The elbow 50 further comprises a planetarygear transmission 520, which, as shown in FIG. 16, is a two-stageplanetary transmission. In an embodiment, the planetary geartransmission 520 is modified from a stock gear offered by MicroMo(Clearwater, Fla.) that increases output torque while reducing speed.The elbow 50 further comprises a non-backdrivable clutch 530 coupled toa differential roller screw 540. In general, differential roller screwssuch as the differential roller screw 540 are useful to convert rotarymotion to linear motion, as it has high efficiency (86%) similar to aball screw, yet can withstand high axial forces, similar to lead screws,that result from the loads experienced by the arm. In one embodiment,the differential roller screw 540 converts the rotary motion of thenon-backdrivable clutch 530 to linear motion. In one embodiment, anon-backdrivable differential roller screw may be used. A thrust housing547 pushes against the differential roller screw 540 when thedifferential roller screw 540 actuates to flex the elbow 50.

A roller screw nut 546 of the differential roller screw 540 pivots abouthinge joint 130 and nut pivot 546, so that the differential roller screw540 experiences axial loads but not bending moments. FIG. 17 shows elbow50 extended and FIG. 18 shows elbow 50 flexed, with differential rollerscrew 540 pivoting about the hinge joint 130. The hinge joint 130 isencased in the bushing 120. In one embodiment, the bushing 120 is madeof a nonlinear compliant material, such as rubber, rather than of arigid material. When made of a nonlinear compliant material, the bushing120's stiffness provides the elbow 50 with joint compliance similar tothat of able-bodied persons when their elbows swing freely duringwalking. As a result, a user who walks while wearing limb 10 using anon-compliant bushing 120 experiences a more natural swinging movement.Additionally, the nonlinear nature of the compliance prevents the jointof the elbow 50 from deforming too far, such as when a user raises thelimb 10 over her head or uses the limb 10 to push herself out of herseat.

In an embodiment, the elbow 50 further comprises the elbow linkage 590shown at FIGS. 19 and 20. In one embodiment, the elbow linkage 590comprises the frame 110, the differential roller screw 540, a humeralframe 544, the roller screw nut 546, the thrust housing 547, a first nutlink 548 and a second nut link 549. However, it should be understoodthat different link configurations could be used to assemble the elbowlinkage 590. The elbow linkage 590 converts the linear motion of thedifferential roller screw 540 to rotary motion about the axis ofrotation 560 of the elbow 50, via force applied thorough the rollerscrew bracket 545 and the roller screw nut 546. A user will typicallyuse the limb 10 while in an upright position. As a result, the torquegenerated by gravitational forces is minimal when the elbow 50 is fullyextended, as shown in FIG. 17, and is maximal when the elbow 50 isflexed 90 degrees. For this reason, the elbow linkage 590 has akinematically defined non-constant gear ratio. The lengths of the fourbars in the elbow linkage 590 may be optimized to minimize the linkageforces and the torque required to lift a constant weight from 0 to 135degree range of motion of the elbow 50. The axis of the elbow linkage590 is placed non-prisimatically relative to socket connector 95, suchthat elbow 50 has a natural carrying angle that mimics the carryingangle in humans. FIG. 19 shows the socket connector 95 at such an angle.As shown in FIG. 19, this carrying angle creates medial humeral rotationwhen the elbow 50 is flexed, allowing the hand 30 to reach the midlineof the body without the need for a separate humeral-rotator. Two shearpins (not shown) connecting the elbow linkage 590 break when the elbow50 is subjected to excessive torque, to prevent potential damage to thedifferential roller screw 540. Excessive torque might result if a userfalls on the limb 10 or from an external force applied to the limb 10.The placing of shear pins allows for the arm to fail gracefully whenneeded. The shear pins may easily be replaced by a clinician or servicetechnician, allowing for relatively inexpensive repair.

FIG. 17 shows elbow 50 in a position of relative extension and FIG. 18shows the elbow 50 in a position of relative flexion. As shown in FIGS.15-20, in one embodiment, the elbow may comprise a first limb portion,which may comprise the humeral frame 544, and a second limb portion,which may comprise the frame 110, coupled together at the elbow joint551. A first end of the screw 540 is coupled to the first limb portion,for instance by threading the first end of the screw 540 through theroller screw nut 546, which is attached to the roller screw bracket 545by the screws 552. The transmission housing 550 is coupled to thehumeral frame 544 at a transmission joint, which in one embodiment isthe hinge joint 130. When the screw 540 extends linearly in a directionaway from the transmission housing 550, the screw 540 applies a force onthe roller screw bracket 545 via the roller screw nut 546, which causesthe humeral frame 544 to rotate about the elbow joint 551 towards thehumeral frame 544. The rotation of the first limb portion towards thesecond limb portion is also known as the flexion of the elbow. When thescrew 540 retracts linearly in a direction towards the transmissionhousing 550, the screw 540 applies a force on the roller screw bracket545 that causes the humeral frame 544 to rotate about the elbow joint551 away from the frame 110. The rotation of the first limb portion awayfrom the second limb portion is also known as the extension of theelbow. In one embodiment, as the screw 540 extends linearly in adirection away from the transmission housing 550, the transmissionhousing 550 rotates about the hinge joint 130 in a first direction. Asshown in FIG. 18 in comparison to FIG. 17, the transmission housing 550rotates about the hinge joint 130 in a clockwise direction indicated byarrow 561. When the screw 540 retracts linearly in a direction towardsthe transmission housing 550, the transmission housing 550 rotates aboutthe hinge joint 130 in a second direction opposite to the firstdirection. As shown in FIG. 17 in comparison to FIG. 18, thetransmission housing 550 rotates about the hinge joint in acounter-clockwise direction indicated by arrow 562.

In some of the embodiments described herein, the limb 10 conforms to thebody size of a 25th percentile adult female (17.8 cm/7″ handcircumference) and has a sufficiently small mass in order to be mostsuitable for smaller users, such as women or children. It should beunderstood that the design of the limb 10 and its associated componentscan be scaled to accommodate other sized users. The components of thelimb 10 described herein may be used with other prostheses components.For instance, the hand 30, the wrist rotator 90, and the wrist flexor 70may be coupled to a prosthetic forearm of another manufacturer.

Each papers and articles noted herein are hereby incorporated byreference and available for inspection in the records of the UnitedStates Patent and Trademark Office for this patent.

In view of the many possible embodiments to which the principles of thepresent discussion may be applied, it should be recognized that theembodiments described herein with respect to the drawing figures aremeant to be illustrative only and should not be taken as limiting thescope of the claims. Therefore, the techniques as described hereincontemplate all such embodiments as may come within the scope of thefollowing claims and equivalents thereof.

What is claimed is:
 1. An elbow for a prosthetic limb, the elbowcomprising: an exterior-rotor motor; a transmission comprising aplanetary gear transmission, a non-backdrivable clutch, and a screw; thescrew adapted to receive a rotational force in a first direction fromthe clutch, and in response to the rotational force in the firstdirection, extend linearly with respect to the transmission so as tocause the elbow to flex.
 2. The elbow of claim 1, wherein the clutchcomprises: a cam comprising an annulus, an input side that is adapted toreceive an input force, and an output side that is adapted to provide anoutput force; a pin and a roller, each located adjacent to the inputside of the cam; wherein the cam is adapted so that movement of the camin response to the input force causes the pin to push the roller out ofcontact with the annulus, when a force is applied to the input side ofthe cam, the pin pushes the roller out of contact with the annulus toallow for movement of the cam.
 3. The elbow of claim 1, furthercomprising: a frame adapted to surround the transmission and having anopening for receiving a battery; a socket connector coupled to theelbow, for attaching the elbow to a prosthetic socket; and a positionsensor for indicating the rotational movement of the elbow.
 4. The elbowof claim 1, wherein the screw is further adapted to receive a rotationalforce in a second direction from the clutch, and in response to therotational force in the second direction, retract linearly with respectto the transmission so as to cause the elbow to extend.
 5. The elbow ofclaim 3, wherein the socket connector is coupled to the elbow at acarrying angle.
 6. The elbow of claim 5, wherein the screw is adifferential roller screw.
 7. The elbow of claim 6, further comprising apivot for the flexion or extension of the elbow, the pivot being encasedin a bushing made of a nonlinear compliant material.
 8. The elbow ofclaim 7, wherein the elbow has a 135 degree range of motion between fullflexion and full extension.
 9. The elbow of claim 8, further comprisinga shear pin.
 10. The elbow of claim 2, further comprising: a first limbportion and a second limb portion coupled together at an elbow joint;wherein a first end of the screw is coupled to the first limb portion ata bracket, and the transmission is coupled to the second limb portion ata transmission joint; wherein when the screw extends and retractslinearly, the screw pivots with respect to the bracket and thetransmission pivots with respect to the second limb portion.
 11. Anelbow component for a prosthetic limb, comprising: a first limb portionand a second limb portion coupled together at an elbow joint; atransmission comprising a screw, wherein a first end of the screw iscoupled to the first limb portion at a bracket; and, the transmission iscoupled to the second limb portion at a transmission joint; wherein thescrew and the hinge are adapted so that: when the screw extends linearlyin a direction away from the transmission, the screw applies a force onthe bracket that causes the first limb portion to rotate about the elbowjoint towards the second limb portion; and when the screw retractslinearly in a direction towards the transmission, the screw applies aforce on the bracket that causes the first limb portion to rotate aboutthe elbow joint away from the second limb portion.
 12. The elbowcomponent of claim 11, wherein the transmission and elbow joint areadapted so that: when the screw extends linearly in a direction awayfrom the transmission, the transmission rotates about the transmissionjoint in a first direction; when the screw retracts linearly in adirection towards the transmission, the transmission rotates about thetransmission joint in a second direction opposite to the firstdirection.
 13. The elbow of claim 12, wherein when the screw extends andretracts linearly, the screw pivots with respect to the bracket and thetransmission pivots with respect to the second limb portion.
 14. Theelbow component of claim 11, wherein the screw extends and retracts inresponse to actuation of the transmission.
 15. The elbow component ofclaim 11, further comprising a position sensor to indicate rotationalmovement of the elbow component.
 16. The elbow component of claim 11,further comprising a bushing made of a nonlinear compliant material thatencases the transmission pivot; a socket connector coupled to either thefirst limb portion or the second limb portion; and a frame thatsurrounds the transmission and is adapted to receive a battery; whereinthe screw is a differential roller screw.
 17. The elbow component ofclaim 16, wherein the socket connector is coupled to the first limbportion at a carrying angle.
 18. The elbow component of claim 13,wherein the screw is coupled to the bracket by a nut.
 19. A transmissionfor an elbow joint of a prosthetic limb, the transmission comprising: amotor, a gear set comprising at least one gear, a non-backdrivableclutch, and a screw, adapted to be housed in a frame pivotally attachedto a second portion of the limb; the screw adapted to be coupled to afirst portion of the limb that is pivotable with respect to the secondportion of the limb; the screw adapted to receive a rotational force ina first direction from the clutch, and in response to the rotationalforce in the first direction, extend linearly with respect to thetransmission; and the screw further adapted to receive a rotationalforce in a second direction from the clutch, and in response to therotational force in the second direction, retract linearly with respectto the transmission.
 20. The transmission of claim 19, wherein thenon-backdrivable clutch comprises: a cam comprising an annulus, an inputside that is adapted to receive an input force, and an output side thatis adapted to provide an output force; a pin and a roller, each locatedadjacent to the input side of the cam; wherein the cam is adapted sothat movement of the cam in response to the input force causes the pinto push the roller out of contact with the annulus, when a force isapplied to the input side of the cam, the pin pushes the roller out ofcontact with the annulus to allow for movement of the cam.
 21. Thetransmission of claim 20, wherein the screw is a differential rollerscrew.